Took my Adventure out yesterday to test the Turbo Fins. I have two drives so I could compare the drives in the exact same conditions. I began with the stock fin drive and pedaled for about a mile to get the kinks out of my legs and set a test rate. I monitored speed with my GPS. I then put in the Turbo Drive (with the tension adjustment set in mid range) and tried to maintain the same amount of exertion. It was all very subjective, but I tried!

Conclusions: As others have mentioned, I liked the feel of the increased resistance and believe the Turbo Fins gave me a good 15% increase in speed. I ended up doing 7.5 miles and had a top speed 8.2 mph (going with the tidal current). Other than being rained on, it was a nice outing and I think the Turbo Fins are keepers!